The editor#

The editor is where a Formula is written and changed. It is in your web app under Formulas, in the demo, and on this site behind Open in the formula gallery and Open in editor under an example. The preview plays as you type.

To get there in your web app, press + New formula, or pick a Formula and press Remix for a bundled one or Edit for one of yours.

The preview#

The preview is at the top, and on a phone it stays in view while you scroll. The line under it says how long the loop is, or that the Formula follows the clock, how often the panel draws it (every refresh, every 2nd or every 4th, with about how many a second: your panel's own figure when one is connected), and how hard it is for the panel: light, medium or heavy. Hover over that line to see the estimate in milliseconds a frame. The preview draws its frames at about the moments the panel would, as far as your screen's own refresh allows.

The rating counts how fast the panel usually draws the Formula. The panel also needs to be able to draw it the slow way, when it can't use its faster path, and refuses a Formula that would take more than about 40 ms a frame that way. (A smooth one past 32 ms is drawn every 2nd refresh instead, and the line under the preview says so.) Such a Formula is rated too heavy, and a line under the preview says so, even when it would usually be light.

The row under the preview holds the time.

• ❚❚ holds the picture still, and ▶ plays on.
• ‹ and › step a frame back or on. With the preview selected, the , and . keys do the same.
• The slider drags through the loop, or through the first 10 seconds of a Formula that goes on without repeating. t is shown beside it.

Edit while the picture is held and the new text is drawn at the same moment.

A Formula that draws over a GIF is shown over a sample picture. Pick a GIF… draws it over one of the GIFs in your playlist or a GIF file from your computer, moving as the GIF does.

When something is wrong#

If the text has a mistake, the editor says what is wrong just above the code, marks the place and keeps playing the last version that worked, dimmed.

• Line N at the start of the message takes you to the line.
• Fix it appears when the message suggests a fix, such as "did you mean t", and writes it in.
• The code at the end, such as E201, opens the language reference's entry for that error.

Changing numbers and colours#

• Drag a number left or right to try other values. On a computer, drag it in the text, or put the cursor on it and press Alt+↑ or Alt+↓. Hold Shift for steps ten times bigger. On a phone, tap a number and drag the bar that appears under the code, or use its − and +. Ctrl+Z (⌘Z on a Mac) undoes a whole drag at once.
• Pick a colour. Each colour in the text, such as #f80, has a bar under it in that colour. Click or tap in one and a swatch appears at the end of its line. The swatch opens your browser's colour picker, and the colour you pick takes the old one's place. Ctrl+Z (⌘Z) puts the old colour back. With the keyboard, put the cursor in the colour and press Esc, then Tab.
• Paint a sprite. With the cursor in a sprite block, press Edit the picture at its first line. The picture opens as a grid. Pick a character from the key, where the checked one is see-through, then click or drag to paint. + Column, − Column, + Row and − Row change its size at the right and the bottom, and + Colour adds a colour to the key. Each stroke goes into the text, and Undo takes it back.
• Edit a palette. With the cursor in a palette line, press Edit the palette. A strip shows its colours as the panel reads them, from left to right. Tap a colour to change it, drag it to move it, give it a name, take it away with ×, or add one with + Colour.

Typing#

• After two letters, a list shows the names that fit. ↑ and ↓ choose, Tab or Enter puts one in, and Esc closes the list. On a phone the names are buttons under the code.
• Inside a function's brackets, a line says what it takes, with the value you are typing in bold.
• Enter keeps the line's indent. After { it starts an indented line and puts the } under it.
• Tab and Shift+Tab indent and unindent. To leave the code with the keyboard, press Esc, then Tab.
• Cheat sheet lists every name in the language with a line about each. Tap a name to put it in.
• A line such as use Plasma as p puts the Formula called Plasma in as a function, p, once the cursor leaves the line. It works for your Formulas and the bundled ones that have a single colour line and no layers, drawing, tables, sprites or palettes. See How Psi thinks.

Settings and controls#

⚙ Settings opens one sheet for what the Formula says about itself. Each change there is a line at the top of the text.

• Name and About are its name and about lines.
• Controls are its sliders and buttons, three at most. + Add a control adds one, and each can be a Slider with a range, a default and a label, or a Choice of two to six words.
• Can be the panel's look lets it be drawn over every GIF, with a Blend and an Amount.

A control line looks like control speed 0..4 = 1 "Speed". speed is the value the Formula reads, from 0 to 4, starting at 1, labelled "Speed". A choice looks like control shape = cube, ring, and shape is 0 for the first word, 1 for the next and so on. A Formula that reads a, b or c without a control line gets a plain slider from 0 to 1 for each.

Try it out#

A Formula that reads the world around the panel, such as daylight, night or replay.game, gets Try it out under the preview. It changes only the preview.

• Time travel moves the sun, the moon and the clock to another moment, with a time of day and a date. Play runs a whole day in about 30 seconds. It uses your panel's location from Settings › Schedule, and London when none is set. Use this browser's location is the other choice.
• Start a game, Back to the menu and Night on make the changes the panel would see, and there is a slider for each value it reads.
• Back to the defaults undoes it all.

Saving and showing#

In your web app, the buttons under the code are these.

• Save (Ctrl+S) keeps it under its name, on your panel when it has a card and in this browser otherwise.
• Show on panel (Ctrl+Enter) plays it on the panel until the playlist moves on. It is there when the web app is your display's own.
• Add to playlist… puts it in one of your playlists.
• Set as the panel's look keeps it over every GIF.
• Save as GIF… makes a GIF of it in Create Art.
• Copy code puts the Formula's text on the clipboard.
• Submit to the gallery… shares it. See Formulas.

On this site the editor has Open on my panel instead of Save, and Copy code and Submit to the gallery… as well. It saves the Formula on your panel under Your formulas and opens it in your web app. Your changes on the site are kept in this browser, and Continue where you left off puts them back when you come back to the Formula. In the demo and on this site, What costs most marks the lines that take the panel the most work, and Tidy up lays the code out the usual way.

Earlier versions… lists the last ten versions of this Formula kept in this browser, from each save and from when it arrived. Tap one to see what going back would change, then Go back to this. Ctrl+Z takes it away again.

‹ Formulas goes back to your Formulas. If you leave without saving, the Formulas view offers Continue editing at the top.